Contact lenses in wide use today fall into two categories. First, there are the hard or rigid corneal type lenses that are formed from materials prepared by the polymerization of acrylic esters, such as polymethylmethacrylate (PMMA). Second, there are the hydrogel or soft type of lenses made by polymerizing hydrophilic monomers such as 2-vinyl pyrrolidone, 2-hydroxyethyl methacrylate (HEMA), or in the case of extended wear, silicone hydrogel contact lenses, by polymerizing silicon-containing monomers or macromonomers with one or more hydrophilic monomers. Solutions that wet the lenses before insertion in the eye are required for both the hard and soft types of contact lenses. After the contact lenses are inserted in the eye, ophthalmic solutions for rewetting, lubricating, and/or enhancing patient comfort (e.g., less dryness, or less end of day irritation) are sometimes applied to the eye by means of a drop dispenser.
Those skilled in the art have long recognized that surface characteristics play a major role in biocompatibility, and more importantly, with a patient's sense of comfort with wearing contact lenses throughout the day and evening. The ionic surface of soft contact lenses can interact with biological components of the tear film, which includes several different ocular proteins, lipids, mucins, and enzymes. The sorption (absorption and adsorption) of tear lipids onto the surface of a contact lens is a common problem and the extent of lipid sorption will depend upon a number of factors including the nature of the lens material from which the lens is made. The accumulation of tear lipids on a lens surface, particularly with frequent replacement lenses (FRPs) or extended-wear lenses (EWs), can lead to dehydration, non-wettability or poor visual quality of the lens and promote tear film instability resulting in patient discomfort.
It is now accepted that increasing the hydrophilicity of the contact lens surface improves the wettability of the contact lenses, which in turn is often associated with improved comfort with wearing contact lenses throughout the day. As stated, the surface of the lens can affect the lens's susceptibility to sorption or accumulation of lipids naturally present in tear fluid. Extended-wear lenses, i.e. lenses used without daily removal of the lens before sleep, present additional challenges. Lipid accumulation can become a significant problem as the lenses must possess a high level comfort and biocompatibility during the time they remain in the eye—in many instance from 7 to 30 days.
Rewetting solutions can improve the comfort of wearing soft contact lenses during the day by increasing the surface wettability, and are added directly to the contact lens in the eye. Such solutions typically contain viscosity enhancing agents, lubricants, surfactants, buffers, preservatives, and salts. For example, U.S. Pat. No. 4,786,436 to Ogunbiyi, et al. describes contact lens wetting solutions that can include collagen and other demulcents such as hydroxylethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxylpropyl-cellulose and the like.
PCT Application (Publication No. WO 01/057172) describes a contact lens care solution that includes a polysaccharide with a molecular weight of 5000 daltons or greater (0.005 to 10 wt. %), a nonionic surfactant (0.01 to 10 wt. %) and a polymeric preservative (0.00001 to 1 wt. %). An exemplary solution is provided as Example No. 5. This solution includes 0.02 wt. % sodium hyaluronate, 1.0 wt. % poloxamine (Tetronics®1107), 0.125 wt. % Na2EDTA and 1 ppm of PHMB in a phosphate buffer. U.S. Pat. No. 5,765,579 to Heiler et al. describes lens care compositions to clean and disinfect contact lenses. The compositions include a sulfobetaine compound to help remove protein deposits from the surface of contact lenses. A preferred sulfobetaine is sulfobetaine 3-10. Lastly, U.S. Pat. Nos. 5,604,189 and 5,773,396 to Zhang et al. describe a composition for cleaning and wetting contact lenses comprising (i) a non-amine polyethyleneoxy-containing compound having an HLB of at least about 18, (ii) a surface active agent having cleaning activity for contact lens deposits that may have an HLB less than 18, and (iii) a wetting agent.
It would, therefore, be desirable to develop a contact lens care solution that could be used to periodically clean and disinfect contact lenses upon removal of the lens from the eye, or a solution applied directly to the eye as in a rewetting solution, that would minimize the sorption of lipids on the lens surface.